Marion and Mary had an equal number of cards at first. Marion used
15 of her cards and Mary used
17 of her cards. They used 72 cards altogether. How many cards did Mary have in the end?
| |
Marion |
Mary |
| Before |
5x7 =
35 u |
7x5 =
35 u |
| Change |
- 1x7 =
- 7 u |
- 1x5 =
- 5 u |
| After |
4x7 =
28 u |
6x5 =
30 u |
The number of cards that Marion and Mary each had at first is the same. Make the number of cards that Marion and Mary each had at first the same. LCM of 5 and 7 is 35.
Number of cards that Marion and Mary used
= 7 u + 5 u
= 12 u
12 u = 72
1 u = 72 ÷ 12 = 6
Number of cards that Mary had in the end
= 30 u
= 30 x 6
= 180
Answer(s): 180
